1. Field of the Invention
The present invention relates to a method of making a composite structure, such as an aircraft air foil, and more particularly to a method of forming a composite structure with a chamber area and a precision opening leading thereto, such as an air foil having capability for boundary layer flow.
2. Brief Description of the Prior Art
In the aircraft industry, it has been found that higher strength to weight ratios can be obtained by use of composite structures where there is a high strength surface sheet, made of material such as titanium or aluminum, and a lower strength base material, such as a graphite impregnated epoxy resin. In some instances, there are advantages in making an aircraft structural component as a relatively large, bonded single structure. One benefit of this is that it eliminates the need of connecting together a number of small sub-components, which quite often entails the use of fasteners. The fasteners in turn cause added weight and require holes for the fasteners, which result in a decrease of strength in the structure. However, some of the manufacturing problems in making such composite structures are quite difficult to resolve. One particularly difficult problem arises where it is desired to form an air foil with the capability for boundary layer control.
It has long been known that the performance of air foils can be enhanced by drawing air in through the surface of the air foil at selected locations, to alleviate the problems of air turbulence adjacent to the air foil surface. This requires the formation of small precision openings or slots in the air foil surface, along with a plenum or some other means to maintain uniform air flow through the slots. For reasons of properly locating the slot and maintaining its width within quite close tolerances, it is desirable that the skin of the air foil first be bonded to the base member before the slot is formed. However, attempting to form a quite narrow precision slot in the sheet member of a composite structure already formed presents other problems, such as properly forming the slot without damaging or impairing the integrity of the overall structure, forming the slot without irregularities or jagged edges which might impair proper airflow therethrough, etc.
In view of the foregoing, it is an object of the present invention to provide a method of making a composite structure, such as an air foil, comprising a base member and a sheet member, secured one to the other and defining therebetween a chamber area, such as an air plenum, where there is a precision opening communicating through the sheet with the chamber area, such as a slot used for boundary layer control on an air foil.